Chemical modification could make nuts safe to eat

The threat of death does not loom over most people who dip their fists in a bowl of honey-roasted cashews. For those with severe nut allergies, however, such a treat can quickly turn into a trip to the emergency room. Now, preliminary research focusing on modifying the protein structures of peanuts and tree nuts could lead to the creation of hypoallergenic nuts that even the severely allergic can enjoy.

Peanuts and tree nuts such as cashews and walnuts cause life-threatening allergic reactions in an estimated 19 million adults and children in the United States. “The only widely accepted practice for preventing an allergic reaction to nuts is strict avoidance—stay away from the food,” notes Christopher Mattison, a molecular biologist with the U.S. Department of Agriculture’s Agricultural Research Service. But because even the most careful nut avoider is still prone to accidentally ingesting one, Mattison decided to look for an alternate solution: changing the food instead of changing the person.

Many nut allergies are triggered when the immune system recognizes specific proteins in the food and releases the antibody immunoglobulin E (IgE) to latch on to the allergen, thereby causing reactions from mild itching to life-threatening anaphylaxis, a whole body reaction that may include an itchy rash, throat swelling, and low blood pressure. Mattison knew that the problem isn’t the release of IgE per se, but rather the myriad allergic reactions triggered when it binds to the nut proteins. So he decided to modify the shape of cashew proteins so that IgE wouldn’t be able to recognize them.

For this preliminary experiment, Mattison and his team treated proteins from cashew extract with a potent combination of heat and sodium sulfite, a chemical often used in food preservation and known to be safe to eat. The treatment essentially cuts the proteins up into smaller pieces, destroying the IgE molecules' ability to recognize them. When the researchers tested the altered proteins by mixing them with IgE taken from people allergic to cashews, about 50% fewer of the IgE bound to the altered proteins compared with when they mixed the IgE with unmodified cashew proteins, they report today at the 248th National Meeting & Exposition of the American Chemical Society in San Francisco, California, and in the 16 July issue of the Journal of Agricultural and Food Chemistry.

Although similar studies had been conducted previously, Mattison’s is the first to use a compound (sodium sulfite) “generally regarded as safe,” or GRAS, by the U.S. Food and Drug Administration rather than harsh chemicals people could never hope to eat. Using a GRAS compound in this process is the only way the altered nuts could eventually be manufactured as a food product, Mattison says. Though that goal is still a long way off, his team is already at work on the next step: modifying whole cashews, rather than cashew extract, to be hypoallergenic. Then they’ll have to turn their attention to making sure the modified cashews taste the same as their allergy-causing cousins, Mattison says. After all, no one wants their snack to have a strange aftertaste.

Such applications may be a long way off, cautions Robert Wood, a pediatric allergist at Johns Hopkins Children’s Center in Baltimore, Maryland. Even the smallest amount of nut protein can set off an allergic reaction in certain patients, he notes. In other words, if even 1% of a patient’s IgE binds to cashew protein, that can still be enough to trigger an allergic reaction. Fifty percent, he says, is still way too dangerous. “My patients would love an allergy-free nut but would have no interest in an allergy-reduced nut.”

A “less allergenic” nut is “not going to change most of my patients’ lives,” agrees J. Allen Meadows, a practicing allergist in Montgomery and spokesman for the American College of Allergy, Asthma & Immunology. Still, he says he would like to see the research continue, as other still-untested GRAS compounds may potentially be able to eradicate all traces of allergen someday. “This is research that is just one step along a long journey.”